The present invention relates generally to radio pagers and, more particularly, to a combined pager/ timepiece applicance that may be worn on the wrist of the user wherein the pager portion thereof is protected from desensitization that may otherwise occur when the associated stepping motor controlling the timepiece is in operation.
In the evolution of radio pagers, miniaturization has become the watchword. The state of the art is now at the point where the pager device may be worn on the wrist of the user. this in turn affords the opportunity to combine such paging device with a timepiece to provide a very useful and highly desirable personalized appliance.
One potential, and perhaps, obvious arrangement of the foregoing type is a pager combined with an analog watch with hour, minute and second hands suitably controlled by a pulsed stepping motor. The stepping motor is conventionally controlled by voltage pulses at regular intervals to increment the second and in turn the minute and hour hands and thereby causing the correct time to be displayed. The voltage pulses may be generated from an internal reference oscillator that also serves a function in the data processing operation of the pager portion of the device or, alternatively, separate oscillators may be provided. It will be appreciated that these reference voltage pulses applied to the associated stepping motor may well result in a degradation in performance regarding the radio pager operation under certain operating conditions. These deleterious effects are usually in the form of RF radiation generated by the stepping motor which results in a desensitization of the paging receiver itself. How severe is dependent upon many factors, but it is fair to note that any desensitization necessarily says that the paging receiver is simply not performing to its designed capability, and therefore undesirable.
Additionally, the varying current drain of the battery may well cause still additional degradation in the paging receiver performance. That is, the variable increase in battery current during stepping motor operation may well reduce the voltage level at the battery terminals which in turn results in less than optimum operating levels for the paging receiver circuitry again, adding to receiver sensitivity degradation.